i have played Ore Imo Portable games on PSP and from what I got told is that

Spoiler Alert! Click to show or hide

They are not actually brother and sister, so no blood relationship, and one of the game route is that Kyousuke and Kirino start to treat each other like lovers

what do you think about kirino's route?

Spoiler Alert! Click to show or hide

The route begins with Krino being the same Tsundere like in the anime, she ends up softening up over time, in the second game, it's pretty blunt that they tell others that they are not blood relatives and still blush when others think they are lovers. While in Kuro neko's route they ended up kissing and got pretty close, Kirino's route did not go too far as Kirino being a tsundere. If you don't mind me spoiling the game, kyosuke went to Tokyo for a school trip where Kirino ask for all Meruru merchandise he can find. When kyosuke came back, she no longer wants them so she threw them away. The ending is just kyosuke convinced kirino that being an otaku isn't bad and she went back to normal again.

i have played Ore Imo Portable games on PSP and from what I got told is that

Spoiler Alert! Click to show or hide

They are not actually brother and sister, so no blood relationship, and one of the game route is that Kyousuke and Kirino start to treat each other like lovers

what do you think about kirino's route?

Spoiler Alert! Click to show or hide

The route begins with Krino being the same Tsundere like in the anime, she ends up softening up over time, in the second game, it's pretty blunt that they tell others that they are not blood relatives and still blush when others think they are lovers. While in Kuro neko's route they ended up kissing and got pretty close, Kirino's route did not go too far as Kirino being a tsundere. If you don't mind me spoiling the game, kyosuke went to Tokyo for a school trip where Kirino ask for all Meruru merchandise he can find. When kyosuke came back, she no longer wants them so she threw them away. The ending is just kyosuke convinced kirino that being an otaku isn't bad and she went back to normal again.